1. Field of the Invention
This invention relates to a drive arrangement for knives employed to spread and thrust ink through printing matrices on silk-screen printing machines.
2. The Prior Art
As is known, the silk-screen printing process involves the use of a matrix or stencil formed of a grid-like fabric, or its equivalent, stretched over a supporting frame. The matrix proper is prepared by blocking meshes of the fabric grid where colorless areas locate, using a variety of techniques which provide, for instance, for the use of special gelatine papers cut to a desired pattern and subsequently hot pressed against the grid-like fabric. The gelatine then melts and blocks the meshes.
Printing is carried out by placing the matrix over a surface to be imprinted which may comprise any of a number of materials, such as cloth, glass, plastics, metal, etc., and pouring ink over it. The ink is then spread and forced through by means of specially provided knives in order to make it to penetrate the open meshes of the grid-like fabric uniformly.
Such known arrangements are generally operated by compressed air, which also provides the motive power for the linkages comprising them. The demand for compressed air may be quite high, especially where plural silk-screen printing stations are provided, as is usually the case with many of the industries employing this printing technique, and it is a well-recognized fact that the components of a compressed air system are fairly critical and require periodic checking and reconditioning of worn parts.
It has also been found that known arrangements cannot always provide for a truly uniform distribution of the ink across the matrix because of their being inadequate to set the knives at suitable inclination angles as the distance of the knives from the matrix changes.
It has been found, moreover, that such known arrangements occasionally fail to permit of a sufficiently accurate adjustment of the distance of the knives from the matrix.